Virus Neutralizing Antibody Titers Research Articles

Serum AZD7442 (tixagevimab-cilgavimab) concentrations and in vitroIC50 values predict SARS-CoV-2 neutralising antibody titres.

The evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) necessitates rapid methods for assessing monoclonal antibody (mAb) potency against emerging variants. Authentic virus neutralisation assays are considered the gold standard for measuring virus-neutralising antibody (nAb) titres in serum. However, authentic virus-based assays pose inherent practical challenges for measuring nAb titres against emerging SARS-CoV-2 variants (e.g. storing infectious viruses and testing at biosafety level-3 facilities). Here, we demonstrate the utility of pseudovirus neutralisation assay data in conjunction with serum mAb concentrations to robustly predict nAb titres in serum. SARS-CoV-2 nAb titres were determined via authentic- and lentiviral pseudovirus-based neutralisation assays using serological data from three AZD7442 (tixagevimab-cilgavimab) studies: PROVENT (NCT04625725), TACKLE (NCT04723394) and a phase 1 dose-ranging study (NCT04507256). AZD7442 serum concentrations were assessed using immunocapture. Serum-based half-maximal inhibitory concentration (IC50) values were derived from pseudovirus nAb titres and serum mAb concentrations, and compared with in vitro IC50 measurements. nAb titres measured via authentic- and lentiviral pseudovirus-based neutralisation assays were strongly correlated for the ancestral SARS-CoV-2 virus and SARS-CoV-2 Alpha. Serum AZD7442 concentrations and pseudovirus nAb titres were strongly correlated for multiple SARS-CoV-2 variants with all Spearman correlation coefficients ≥ 0.78. Serum-based IC50 values were similar to in vitro IC50 values for AZD7442, for ancestral SARS-CoV-2 and Alpha, Delta, Omicron BA.2 and Omicron BA.4/5 variants. These data highlight that serum mAb concentrations and pseudovirus in vitro IC50 values can be used to rapidly predict nAb titres in serum for emerging and historical SARS-CoV-2 variants.

Investigation of the immunomodulatory effect of inactive parapoxvirus (iPPVO) on infectious bovine rhinotracheitis (IBR) vaccine in cattle

In the study, alterations in antibody titers, proinflammatory and antiinflammatory cytokine levels were determined in serum samples collected at various periods before and after administration of inactive IBR and iPPVO to cattle. It was aimed to investigate the immunomodulatory effects of inactivated parapoxvirus ovis (iPPVO) in cattle vaccinated with inactivated-IBR vaccine. In the study, 40 unvaccinated, clinically healthy cattle of different breeds aged older then 3 months were used. Three groups of cattle were formed as control group 1 (n=10), control group 2 (n=10) and experimental group (n=20). iPPVO was applied to the cattle in the control group 1 and experimental groups on the 0, 2nd, and 4th days. Blood samples were colleted from all the animals after 6th hours of the injections applied on 0th and 4th days of the study. Commercially available ELISA kits were used to determine serum levels of of IL-2, IL-6, IL-12 and IFN-γ. Furthermore, virus neutralization test was also performed to detect virus neutralizing antibody titres. In the present study, serum levels of IL-2, IL-6 IL-12, and IFN-γ levels were found to be significantly higher in the experimental group compared to that of the control group 1 and control group 2 (p<0,05). The differences between control group 1 and control group 2 groups were not statistically significant. In conclusion, iPPVO increased the levels of cytokines in IBR vaccinated cattle due to its immunomodulatory effects. In addition, virüs neutralizing antibody titers were found to be significantly higher in cattle that received vaccine and iPPVO.

1363. Preliminary Safety Results from a Phase 1 First in Human Study of VYD222: an Extended Half-Life Monoclonal Antibody (mAb) in Development for COVID-19 Prevention

Abstract Background VYD222 is a fully human IgG1 mAb demonstrating broad and potent in vitro neutralizing activity across SARS-CoV-2 variants including XBB.1.5. VYD222 is a re-engineered version of adintrevimab, an Fc-modified mAb that has a robust safety data package and demonstrated clinically meaningful results in Phase 2/3 clinical trials for both treatment and prevention of COVID-19 (NCT04805671, NCT04859517). VYD222 is currently in development for COVID-19 prevention. Methods This is an ongoing Phase 1, first in human, blinded, randomized, placebo (PBO)-controlled, single ascending dose study of VYD222 administered as slow intravenous (IV) push to healthy adults aged 18-65 years (NCT05791318). Participants were randomized 8:2 in each of 3 cohorts (n=8 VYD222, n=2 PBO): VYD222 1500 mg, 2500 mg, and 4500 mg. Safety and tolerability will be assessed as incidence of treatment emergent adverse events, including serious adverse events (SAEs). Serum pharmacokinetic (PK) parameters will be calculated for VYD222 using noncompartmental analysis methods. Serum virus neutralizing antibody (sVNA) titers of VYD222 ex vivo against relevant SARS-CoV-2 variants will be assessed using a validated assay. Safety, tolerability, PK, and sVNA titers will be assessed through 12 months post-dose. Here we report preliminary blinded safety results from cohorts 1 and 2. Results Overall, 12 participants received VYD222 or PBO. Through a minimum of 14 days post dose, among 10 participants in cohort 1 (VYD222 1500 mg n=8, PBO n=2), there were 9 AEs (adverse events) reported, all of which were mild in severity and considered unrelated to study drug. No participant experienced SAEs, infusion-related reactions, or hypersensitivity reactions. Through 2 days post dose, 2 sentinel participants in cohort 2 (VYD222 2500 mg n=1, PBO n=1) experienced zero AEs, study drug related AEs, SAEs, infusion-related reactions, or hypersensitivity reactions. Enrollment continues in cohort 2 as of the data cutoff (04/25/2023) for this abstract. Data remain blinded currently. Conclusion To date, a single dose of VYD222, up to 2500 mg IV push, was well tolerated across all healthy participants receiving either VYD222 or PBO in this ongoing phase 1 study. These findings support continued clinical development of VYD222. Disclosures Kathryn Mahoney, PharmD, Invivyd, Inc.: Employee|Invivyd, Inc.: Stocks/Bonds Deepali Gupta, BSc, Invivyd, Inc.: Employee|Invivyd, Inc.: Stocks/Bonds Yong Li, PhD, Invivyd, Inc.: Employee|Invivyd, Inc.: Stocks/Bonds Natalia Betancourt, MS, Invivyd, Inc.: Employee|Invivyd, Inc.: Stocks/Bonds Aanika Das, PharmD, Invivyd, Inc.: Employee|Invivyd, Inc.: Stocks/Bonds Ed Campanaro, MS, Invivyd, Inc.: Employee|Invivyd, Inc.: Stocks/Bonds Pete Schmidt, MD, Invivyd, Inc.: Employee|Invivyd, Inc.: Stocks/Bonds

Pseudoneutralizing test for preclinical studies of vaccines against SARS-CoV-2

The purpose of this study was to evaluate efficiency of a competitive enzyme immunoassay which specifically detects antibodies that recognize the receptor-binding domain at the S1 subunit of SARS-CoV-2 coronavirus spike protein and block the formation of initiator infection complex between RBD and angiotensinconverting enzyme 2 (pseudo-neutralizing test, PNT) being applied at the stage of preclinical studies of anti- SARS-CoV-2 vaccine. We studied 37 animal blood sera (8 cows, 10 dogs) as well as 19 male and female transgenic mice of the B6.Cg-Tg(K18-ACE2)2Prlmn/HEMI line hemizygous for Tg(K18-ACE2)2Prlmn (Jackson Immunoresearch, West Grove, PA, USA)) immunized with candidate COVID-19 vaccine preparations containing SARS-CoV-2 Spike protein. In this study, 3 techniques were used for detection of antibodies to SARS-CoV-2 virus, as follows: 1) a pseudo-neutralizing test (PNT) to detect antibodies that block interaction between RBD and ACE-2; 2) neutralization test (RN) to detect virus-neutralizing antibodies, and 3) enzyme-linked immunosorbent assay to detect class G antibodies to RBD SARS-CoV-2. The results were expressed, respectively, as the suppression quotients (SC), titers of virus-neutralizing antibodies (VNA), and the positivity index (IP). The data obtained show a pronounced, statistically significant correlation between the results obtained by immunoassay methods with VNA titers determined in the studied animals by the virological neutralization test. E.g., the Spearman correlation quotients for VNA and SC titers, were, respectively, 0.9151; 0.8085, and 0.9207 for dogs, transgenic mice and cows. The Spearman quotient for VNA and PI titers was 0.8854 and 0.8955 for dogs and transgenic mice. Thus, in order to evaluate immunogenicity of vaccine preparations in our study, both methods are adequate and safe analogues to RN-ELISA for determination of IgG to RBD and PNT aoming for detection of antibodies blocking the formation of RBD/ACE-2 complex. However, the advantage of PNT is its versatility, eliminating the need to use different conjugates to detect antibodies in blood sera of different animal species. The data obtained for samples of three animal species (transgenic mice, dogs and cows) well agree with similar data obtained by us and other researchers for human blood sera, thus demonstrating high correlation between the results of PNT-like competitive tests to determine antibodies that block the formation of the RBD/ACE-2 complex, with VNA results in virologic neurtralization test (RN). Therefore, the proposed PNT technique may be used in preclinical and clinical trials of candidate vaccines and drugs.

Safety and immunogenicity of three dose levels of an investigational, highly purified Vero cell rabies vaccine: A randomized, controlled, observer-blinded, Phase II study with a simulated post-exposure regimen in healthy adults

ABSTRACT A serum-free, highly purified rabies vaccine produced in Vero cells is under development. The initial formulation, PVRV-NG, was evaluated in five Phase II studies and subsequently reformulated (PVRV-NG2). This multicenter, observer-blinded Phase II study investigated the safety and immune response of three different doses (antigen content) of PVRV-NG2 versus a licensed human diploid cell rabies vaccine (HDCV; Imovax rabies®). Healthy adults (N = 320) were randomized to receive PVRV-NG2 (low, medium, or high dose), PVRV-NG, or HDCV (2:2:2:1:1 ratio), according to a five-dose Essen simulated post-exposure regimen (Days [D] 0, 3, 7, 14, and 28). All participants received human rabies immunoglobulin intramuscularly on D0. Immunogenicity was assessed at D0, 14, 28, 42, and 6 months after the final injection using the rapid fluorescent focus inhibition test. Seroconversion rates were calculated as the percentage of participants achieving rabies virus neutralizing antibody titers ≥0.5 IU/mL. All analyses were descriptive. At each timepoint, geometric mean titers (GMTs) increased with antigen content (measured using an enzyme-linked immunosorbent assay). High-dose PVRV-NG2 GMTs were the highest at all timepoints, medium-dose PVRV-NG2 GMTs were similar to those with HDCV, and low-dose PVRV-NG2 GMTs were similar to PVRV-NG. The safety profile of PVRV-NG2 was comparable to PVRV-NG; however, fewer injection site reactions were reported with PVRV-NG2 or PVRV-NG (range 36.7–47.5%) than with HDCV (61.5%). This study demonstrated a dose–effect of antigen content at all timepoints. As post-exposure prophylaxis, the safety and immunogenicity profiles of the high-dose PVRV-NG2 group compared favorably with HDCV. Clinicaltrials.gov number: NCT03145766.

Construction and Development of New Rabies Virus Vectors Carrying Enhanced Green Fluorescent Protein

Aim: Rabies is one of the most lethal viral diseases. This study developed a recombinant rabies virus, PVEGFP, expressing an EGFP protein based on PV strain to be applied in virus-neutralizing antibody (VNA) titration methods. Methods: The EGFP gene was inserted into the PVMCS strain, a previously discussed recombinant virus. The recombinant virus was applied in the rapid fluorescent focus inhibition test (RFFIT) VNA titration method, and six vaccinated persons were studied for validation. Results: The recombinant rabies strain showed similar propagation properties to its ancestry strain, PVMCS. It could also measure VNA titers in the RFFIT method not significantly different from those acquired using the CVS-11 virus. Conclusion: Utilizing the PVEGFP strain in the RFFIT method can produce rapid, reliable and affordable results.

Carbohydrate fatty acid monosulphate ester is a potent adjuvant for low-dose seasonal influenza vaccines

There is still a need for a better and affordable seasonal influenza vaccine and the use of an adjuvant could solve both issues. Therefore, immunogenicity of a combination of low dose of 1/5TH (3 µg of HA) a licensed seasonal flu vaccine with the novel carbohydrate fatty acid monosulfate ester (CMS)-based adjuvant was investigated in ferrets and safety in rabbits. Without CMS, hemagglutination inhibition (HI) antibody titers ranged from ≤5 to 26 three weeks post immunization 1 (PV-1) and from 7 to 134 post-immunization 2 (PV-2) in ferrets. Virus neutralizing (VN) antibody titers ranged from 20 to 37 PV-1 and from 21 to 148 PV-2. CMS caused 10 to 111- fold increase in HI titers and 3 to 58- fold increase in VN titers PV-1 and PV-2, depending on influenza strain and dose of adjuvant. Eight mg of CMS generated significantly higher antibody titers than 1 or 4 mg, while 1 and 4 mg induced similar responses.Three µg of HA plus 4 mg of CMS was considered the highest human dose and safety of two-fold this dose was determined in acute and repeated-dose toxicity studies in rabbits conducted according to OECD GLP guidelines. The test item did not elicit any clinical signs, local reactions, effect on body weight, effect on urine parameters, effect on blood biochemistry, or gross pathological changes. In blood, increased numbers of neutrophils, lymphocytes and/or monocytes were noted and in iliac lymph nodes, increased cellularity of macrophages of minimal to mild degree were observed. In both ferrets and rabbits, body temperature increased with increasing dose of CMS to a maximum of 1 ˚C during the first day post-immunization, which returned to normal values during the second day. In the local tolerance study, histopathology of the site of injection at 7 days PV-1 revealed minimal, mild or moderate inflammation in 5, 8 and 5 animals, respectively. In the repeated-dose study and 21 days PV-3, minimal, mild or moderate inflammation was observed in 15, 18 and 3 animals, respectively. We concluded that the data show CMS is a potent and safe adjuvant ready for further clinical development of a seasonal influenza vaccine and combines high immunogenicity with possible antigen-sparing capacity.

A single immunization with core–shell structured lipopolyplex mRNA vaccine against rabies induces potent humoral immunity in mice and dogs

ABSTRACT The persistence and clinical consequences of rabies virus (RABV) infection have prompted global efforts to develop a safe and effective vaccines against rabies. mRNA vaccines represent a promising option against emerging and re-emerging infectious diseases, gaining particular interest since the outbreak of COVID-19. Herein, we report the development of a highly efficacious rabies mRNA vaccine composed of sequence-modified mRNA encoding RABV glycoprotein (RABV-G) packaged in core–shell structured lipopolyplex (LPP) nanoparticles, named LPP-mRNA-G. The bilayer structure of LPP improves protection and delivery of RABV-G mRNA and allows gradual release of mRNA molecules as the polymer degrades. The unique core–shell structured nanoparticle of LPP-mRNA-G facilitates vaccine uptake and demonstrates a desirable biodistribution pattern with low liver targeting upon intramuscular immunization. Single administration of low-dose LPP-mRNA-G in mice elicited potent humoral immune response and provided complete protection against intracerebral challenge with lethal RABV. Similarly, single immunization of low-dose LPP-mRNA-G induced high levels of virus-neutralizing antibody titers in dogs. Collectively, our data demonstrate the potential of LPP-mRNA-G as a promising next-generation rabies vaccine used in human and companion animals.

Preinfection Neutralizing Antibodies, Omicron BA.5 Breakthrough Infection, and Long COVID: A Propensity Score-Matched Analysis.

Data are limited on the role of preinfection humoral immunity protection against Omicron BA.5 infection and long coronavirus disease (COVID) development. We conducted nested case-control analysis among tertiary hospital staff in Tokyo who donated blood samples in June 2022 (1 month before Omicron BA.5 wave), approximately 6 months after receiving a third dose of COVID-19 mRNA vaccine. We measured live virus-neutralizing antibody titers against wild type and Omicron BA.5, and anti-receptor-binding domain (RBD) antibody titers at preinfection, and compared them between cases and propensity-matched controls. Among the breakthrough cases, we examined association between preinfection antibody titers and incidence of long COVID. Preinfection anti-RBD and neutralizing antibody titers were lower in cases than controls. Neutralizing titers against wild type and Omicron BA.5 were 64% (95% confidence interval [CI], 42%-77%) and 72% (95% CI, 53%-83%) lower, respectively, in cases than controls. Individuals with previous Omicron BA.1/BA.2 infections were more frequent among controls than cases (10.3% vs 0.8%), and their Omicron BA.5 neutralizing titers were 12.8-fold higher than infection-naive individuals. Among cases, preinfection antibody titers were not associated with incidence of long COVID. Preinfection immunogenicity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may play a role in protecting against the Omicron BA.5 infection but not preventing long COVID.

Does Perioperative Administration of Rabies Vaccine in Dogs Undergoing Surgical Sterilization Induce an Adequate Antibody Response?

High-volume spay/neuter events may facilitate access to free-roaming dogs to administer rabies vaccination, but important questions remain regarding the effect of surgery and anesthesia on the immune response to a vaccine administered in the perioperative period. This study evaluated the immunogenicity of primary rabies vaccination in dogs when administered during the immediate perioperative period at the time of surgical sterilization (ovariohysterectomy/orchidectomy). Healthy dogs of both sexes presenting for surgical sterilization who had never been vaccinated against rabies virus were eligible for enrollment in the study. Fifty dogs ranging in age from 5 to 96 months were enrolled and were vaccinated against rabies virus during the recovery period following anesthesia and surgery. Rabies virus neutralizing antibody (RVNA) titers were measured preoperatively and 28 days postoperatively. This cohort was compared to a historical control cohort of 57 dogs who received primary rabies vaccination for travel purposes and had RVNA titers measured at the same laboratory as the study group 28-35 days post-vaccination. After controlling for age and sex, there was no statistically significant difference in immunogenicity of a rabies vaccine administered to dogs during the perioperative period in comparison to dogs that received the rabies vaccine for travel alone in the absence of surgery. Perioperative administration of a rabies vaccine in dogs undergoing surgical sterilization induces an adequate antibody response. We recommend that rabies vaccine be administered perioperatively during spay/neuter campaigns in canine rabies endemic areas if other opportunities to access veterinary care and rabies vaccination are limited.

Immunological profile of mice immunized with a polyvalent virosome-based influenza vaccine

BackgroundInfluenza A virus (IAV) causes respiratory disease in pigs and is a major concern for public health. Vaccination of pigs is the most successful measure to mitigate the impact of the disease in the herds. Influenza-based virosome is an effective immunomodulating carrier that replicates the natural antigen presentation pathway and has tolerability profile due to their purity and biocompatibility.MethodsThis study aimed to develop a polyvalent virosome influenza vaccine containing the hemagglutinin and neuraminidase proteins derived from the swine IAVs (swIAVs) H1N1, H1N2 and H3N2 subtypes, and to investigate its effectiveness in mice as a potential vaccine for swine. Mice were immunized with two vaccine doses (1 and 15 days), intramuscularly and intranasally. At 21 days and eight months later after the second vaccine dose, mice were euthanized. The humoral and cellular immune responses in mice vaccinated intranasally or intramuscularly with a polyvalent influenza virosomal vaccine were investigated.ResultsOnly intramuscular vaccination induced high hemagglutination inhibition (HI) titers. Seroconversion and seroprotection (> 4-fold rise in HI antibody titers, reaching a titer of ≥ 1:40) were achieved in 80% of mice (intramuscularly vaccinated group) at 21 days after booster immunization. Virus-neutralizing antibody titers against IAV were detected at 8 months after vaccination, indicating long-lasting immunity. Overall, mice immunized with the virosome displayed greater ability for B, effector-T and memory-T cells from the spleen to respond to H1N1, H1N2 and H3N2 antigens.ConclusionsAll findings showed an efficient immune response against IAVs in mice vaccinated with a polyvalent virosome-based influenza vaccine.

Blockade-of-Binding Activities toward Envelope-Associated, Type-Specific Epitopes as a Correlative Marker for Dengue Virus-Neutralizing Antibody.

Humans infected with dengue virus (DENV) acquire long-term protection against the infecting serotype, whereas cross-protection against other serotypes is short-lived. Long-term protection induced by low levels of type-specific neutralizing antibodies can be assessed using the virus-neutralizing antibody test. However, this test is laborious and time-consuming. In this study, a blockade-of-binding enzyme-linked immunoassay was developed to assess antibody activity by using a set of neutralizing anti-E monoclonal antibodies and blood samples from dengue virus-infected or -immunized macaques. Diluted blood samples were incubated with plate-bound dengue virus particles before the addition of an enzyme-conjugated antibody specific to the epitope of interest. Based on blocking reference curves constructed using autologous purified antibodies, sample blocking activity was determined as the relative concentration of unconjugated antibody that resulted in the same percent signal reduction. In separate DENV-1-, -2-, -3-, and -4-related sets of samples, moderate to strong correlations of the blocking activity with neutralizing antibody titers were found with the four type-specific antibodies 1F4, 3H5, 8A1, and 5H2, respectively. Significant correlations were observed for single samples taken 1 month after infection as well as samples drawn before and at various time points after infection/immunization. Similar testing using a cross-reactive EDE-1 antibody revealed a moderate correlation between the blocking activity and the neutralizing antibody titer only for the DENV-2-related set. The potential usefulness of the blockade-of-binding activity as a correlative marker of neutralizing antibodies against dengue viruses needs to be validated in humans. IMPORTANCE This study describes a blockade-of-binding assay for the determination of antibodies that recognize a selected set of serotype-specific or group-reactive epitopes in the envelope of dengue virus. By employing blood samples collected from dengue virus-infected or -immunized macaques, moderate to strong correlations of the epitope-blocking activities with the virus-neutralizing antibody titers were observed with serotype-specific blocking activities for each of the four dengue serotypes. This simple, rapid, and less laborious method should be useful for the evaluation of antibody responses to dengue virus infection and may serve as, or be a component of, an in vitro correlate of protection against dengue in the future.

Safety and immunogenicity of rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine against SARS-CoV-2 in healthy adolescents: an open-label, non-randomized, multicenter, phase 1/2, dose-escalation study.

ClinicalTrials.gov, NCT04954092, LP-007632.

Limosilactobacillus reuteri DSM 17938 supplementation and SARS-CoV-2 specific antibody response in healthy adults: a randomized, triple-blinded, placebo-controlled trial

ABSTRACT Studies have shown that probiotics can decrease the symptoms of respiratory tract infections as well as increase antibody responses following certain vaccinations. We examined the effect of probiotic supplementation on anti-SARS-CoV-2 specific antibody responses upon SARS-CoV-2 infection as well as after COVID-19 vaccination. In this randomized, triple-blinded, placebo-controlled intervention study with a parallel design, 159 healthy adults without prior SARS-CoV-2 infection or COVID-19 vaccination and any known risk factors for severe COVID-19 were randomly allocated into two study arms. The active treatment arm consumed a probiotic product containing a minimum of 1 × 108 colony-forming units of Limosilactobacillus reuteri DSM 17938 + 10 μg vitamin D3 twice daily for 6 months. The placebo arm consumed identical tablets containing only 10 μg vitamin D3. Anti-SARS-CoV-2 specific antibodies and virus neutralizing antibody titers were analyzed from blood samples collected at baseline, after 3 months, and after 6 months. Differences in serum antibody titers between the two study arms were tested with independent t-test using log-transformed values. In the intention-to-treat (ITT) analysis, SARS-CoV-2 infected individuals in the active treatment arm (n = 6) tended to have higher serum anti-spike IgG (609 [168–1480] BAU/ml vs 111 [36.1–1210] BAU/ml, p = 0.080) and anti-receptor binding domain (RBD) IgG (928 [212–3449] BAU/ml vs (83.7 [22.8–2094] BAU/ml, p = 0.066) levels than individuals in the placebo arm (n = 6). Considering individuals who were fully vaccinated with mRNA-based COVID-19 vaccines, the active treatment arm (n = 10) exhibited significantly higher serum levels of anti-RBD IgA (135 [32.9–976] BAU/ml vs 61.3 [26.7–97.1] BAU/ml, p = 0.036) than the placebo arm (n = 7) >28 days postvaccination. Supplementation with specific probiotics might improve the long-term efficacy of mRNA-based COVID-19 vaccines via enhanced IgA response.

COVID-19 booster vaccination during pregnancy enhances maternal binding and neutralizing antibody responses and transplacental antibody transfer to the newborn

The immune response to COVID-19 booster vaccinations during pregnancy for mothers and their newborns and the functional response of vaccine-induced antibodies against Omicron variants are not well characterized. We conducted a prospective, multicenter cohort study of participants vaccinated during pregnancy with primary or booster mRNA COVID-19 vaccines from July 2021 to January 2022 at 9 academic sites. We determined SARS-CoV-2 binding and live virus and pseudovirus neutralizing antibody (nAb) titers pre- and post-vaccination, and at delivery for both maternal and infant participants. Immune responses to ancestral and Omicron BA.1 SARS-CoV-2 strains were compared between primary and booster vaccine recipients in maternal sera at delivery and in cord blood, after adjusting for days since last vaccination.A total of 240 participants received either Pfizer or Moderna mRNA vaccine during pregnancy (primary 2-dose series: 167; booster dose: 73). Booster vaccination resulted in significantly higher binding and nAb titers, including to the Omicron BA.1 variant, in maternal serum at delivery and in cord blood compared to a primary 2-dose series (range 0.44–0.88 log10 higher, p < 0.0001 for all comparisons). Live virus nAb to Omicron BA.1 were present at delivery in 9 % (GMT ID50 12.7) of Pfizer and 22 % (GMT ID50 14.7) of Moderna primary series recipients, and in 73 % (GMT ID50 60.2) of mRNA boosted participants (p < 0.0001), although titers were significantly lower than to the D614G strain. Transplacental antibody transfer was efficient for all regimens with median transfer ratio range: 1.55–1.77 for IgG, 1.00–1.78 for live virus nAb and 1.79–2.36 for pseudovirus nAb. COVID-19 mRNA vaccination during pregnancy elicited robust immune responses in mothers and efficient transplacental antibody transfer to the newborn. A booster dose during pregnancy significantly increased maternal and cord blood binding and neutralizing antibody levels, including against Omicron BA.1. Findings support the use of a booster dose of COVID-19 vaccine during pregnancy.

Association of fat-soluble vitamins (A, D, and E) status with humoral immune response to COVID-19 inactivated vaccination.

Fat-soluble vitamins (A, D, and E) are essential for the proper functioning of the immune system and are of central importance for infection risk in humans. Vitamins A, D, and E have been reported to be associated with the immune response following vaccination; however, their effects on the immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination remain unknown. We measured the neutralizing antibody titers against wild type and omicron within 98 days after the third homologous boosting shot of inactivated SARS-CoV-2 vaccine (BBIBP-CorV or CoronaVac) in 141 healthy adults in a prospective, open-label study. High-performance liquid chromatography-tandem mass spectroscopy was used to determine the concentrations of plasma vitamins A, D, and E. We found that the anti-wide-type virus and anti-omicron variant antibody levels significantly increased compared with baseline antibody levels (P < 0.001) after the third vaccination. 25(OH)D3 was significantly negatively associated with the baseline anti-wide-type virus antibody concentrations [beta (95% CI) = -0.331 (-0.659 ~ -0.003)] after adjusting for covariates. A potentially similar association was also observed on day 98 after the third vaccination [beta (95% CI) = -0.317 (-0.641 ~ 0.007)]. After adjusting for covariates, we also found that 25(OH)D3 was significantly negatively associated with the seropositivity of the anti-omicron variant antibody at day 98 after the third vaccination [OR (95% CI) = 0.940 (0.883 ~ 0.996)]. The association between plasma 25(OH)D3 with anti-wild-type virus antibody levels and seropositivity of anti-omicron variant antibodies were persistent in subgroup analyses. We observed no association between retinol/α-tocopherol and anti-wide-type virus antibody levels or anti-omicron variant antibody seropositive in our study. The third inactivated SARS-CoV-2 vaccination significantly improved the ability of anti-SARS-CoV-2 infection in the human body. Higher vitamin D concentrations could significantly decrease the anti-wide-type virus-neutralizing antibody titers and anti-omicron variant antibody seropositive rate after the inactivated SARS-CoV-2 vaccination in people with adequate levels of vitamin D, better immune status, and stronger immune response; further studies comprising large cohorts of patients with different nutritional status are warranted to verify our results.

A rationally designed combined intranasal adjuvant drives robust and broad humoral, cellular, and mucosal immune responses to SARS-CoV-2

Abstract Multiple FDA-approved SARS-CoV-2 vaccines have provided excellent protection against severe disease. Despite this, immunity can wane relatively fast, particularly in the elderly and novel viral variants capable of evading infection- and vaccination-induced immunity continue to emerge. Furthermore, while these parenteral vaccines have provided substantial protection, they have been less effective in inducing mucosal immune responses which are critical for effectively blocking viral transmission in vaccinated individuals. As mucosal immune responses are most effectively induced through infection or mucosal immunization, we have developed an intranasal, rationally designed adjuvant integrating a nanoemulsion (NE) that activates TLRs and NLRP3 with an RNA agonist of RIG-I (IVT DI). Through activating this array of receptors, we have shown that the NE/IVT adjuvant better recapitulates the innate immune activation events that occur during natural viral infection, subsequently leading to more tailored and effective downstream adaptive immune responses. The combination adjuvant with various spike protein antigens elicited robust protective humoral, mucosal, and cellular responses to SARS-CoV-2 in mice, with markedly enhanced T H1-biased cellular responses and high virus-neutralizing antibody titers towards both homologous and antigenically distant drift variants of SARS-CoV-2. These results highlight the potential of this adjuvant to improve the immune profile of a variety of SARS-CoV-2 vaccine candidates for use mucosally. This research was supported by R01-AI160706 to P.W. and M.S, and in part by R01-DK130425 to M.S.

Comparative Evaluation of Intradermal vis-à-vis Intramuscular Pre-Exposure Prophylactic Vaccination against Rabies in Cattle.

Rabies is a progressively fatal viral disease affecting a wide variety of warm-blooded animals and human beings. With cattle being major part of Indian livestock population, rabies can result in significant financial losses. Immunization of livestock vulnerable to exposure is the best way to control rabies. The present study was undertaken to investigate the efficacy of a rabies pre-exposure prophylactic vaccine administered through different routes and to sequentially monitor the levels of rabies virus-neutralizing antibody (RVNA) titers in cattle. Thirty cattle were divided into five groups of six animals each. Group I and III animals were immunized with 1 mL and 0.2 mL of rabies vaccine through intramuscular (IM) and intradermal (ID) routes, respectively, on day 0, with a booster dose on day 21; Group II and IV animals were immunized with 1 mL and 0.2 mL of rabies vaccine, respectively, without the booster dose; unvaccinated animals served as a control (Group V). Serum samples were collected on days 0, 14, 28, and 90 to estimate RVNA titers using the rapid fluorescent focus inhibition test (RFFIT). The titers were above an adequate level (≥0.5 IU/mL) on day 14 and maintained up to 90 days in all animals administered the rabies vaccine through the IM and ID route with or without a booster dose. The study indicated that both routes of vaccination are safe and effective in providing protection against rabies. Hence, both routes can be considered for pre-exposure prophylaxis. However, the ID route proved to be more economical due to its dose-sparing effect.

Immunogenicity of a new inactivated vaccine against feline panleukopenia virus, calicivirus, and herpesvirus-1 for cats

Feline panleukopenia virus (FPV), feline calicivirus (FCV), and feline herpesvirus type-1 (FHV-1) are major infectious pathogens in cats. We evaluated the immunogenicity of a new vaccine containing inactivated FPV, two FCVs, and FHV-1 in animals. An FPV, two FCVs, and an FHV-1 isolate were continuously passaged 70, 50, 80, and 100 times in CRFK cells. FP70, FC50, FC80, and FH100 were propagated and used as vaccine antigens. Two inactivated feline virus vaccines, Rehydragel-adjuvanted vaccine (FRAV) and Cabopol-adjuvanted vaccine (FCAV) were prepared and inoculated into mice and guinea pigs. Humoral immune responses were measured using hemagglutination inhibition (HI) for FPV and virus-neutralizing antibody (VNA) for two FCVs and FHV-1 tests. Serial passages in CRFK cells resulted in increase in titers of FPV and two FCVs but not FHV-1 The FCAV induced higher mean HI and VNA titers than the FRAV in guinea pigs; therefore, the FCAV was selected. Cats inoculated with FCAV developed a mean HI titer of 259.9 against FPV, and VNA titers of 64, 256, and 3.2 against FCV17D03, FCV17D283, and FHV191071, respectively. Therefore, cats inoculated with the FCAV showed a considerable immune response after receiving a booster vaccination.

Longitudinal analysis of SARS-CoV-2 reinfection reveals distinct kinetics and emergence of cross-neutralizing antibodies to variants of concern.

The ongoing evolution of SARS-CoV-2 continues to raise new questions regarding the duration of immunity to reinfection with emerging variants. To address these knowledge gaps, controlled investigations in established animal models are needed to assess duration of immunity induced by each SARS-CoV-2 lineage and precisely evaluate the extent of cross-reactivity and cross-protection afforded. Using the Syrian hamster model, we specifically investigated duration of infection acquired immunity to SARS-CoV-2 ancestral Wuhan strain over 12 months. Plasma spike- and RBD-specific IgG titers against ancestral SARS-CoV-2 peaked at 4 months post-infection and showed a modest decline by 12 months. Similar kinetics were observed with plasma virus neutralizing antibody titers which peaked at 2 months post-infection and showed a modest decline by 12 months. Reinfection with ancestral SARS-CoV-2 at regular intervals demonstrated that prior infection provides long-lasting immunity as hamsters were protected against severe disease when rechallenged at 2, 4, 6, and 12 months after primary infection, and this coincided with the induction of high virus neutralizing antibody titers. Cross-neutralizing antibody titers against the B.1.617.2 variant (Delta) progressively waned in blood over 12 months, however, re-infection boosted these titers to levels equivalent to ancestral SARS-CoV-2. Conversely, cross-neutralizing antibodies to the BA.1 variant (Omicron) were virtually undetectable at all time-points after primary infection and were only detected following reinfection at 6 and 12 months. Collectively, these data demonstrate that infection with ancestral SARS-CoV-2 strains generates antibody responses that continue to evolve long after resolution of infection with distinct kinetics and emergence of cross-reactive and cross-neutralizing antibodies to Delta and Omicron variants and their specific spike antigens.